A wiring rule in a ferroelectric memory (FeRAM) is 0.35 μm recently, and in formation of an interlayer insulation film, a plasma CVD method is mainly adopted.
In order to prevent hydrogen diffusion into a ferroelectric capacitor, an alumina film directly covering the ferroelectric capacitor is formed as a hydrogen diffusion prevention film in a ferroelectric memory.
However, miniaturization is also highly demanded of a ferroelectric memory recently, and with miniaturization, the specifications of the ferroelectric capacitor and wiring become rigid. Meanwhile, coverage of an alumina film is comparatively low. For the above reasons, it cannot be said that protection of the ferroelectric capacitor is sufficient, and deterioration of the ferroelectric capacitor becomes a problem.
Concerning an interlayer insulation film, a gap is sometimes generated in the interlayer insulation film between a ferroelectric capacitor and wiring or the like when a multilayered wiring structure is formed. Therefore, high reliability is difficult to obtain.
Further, high moisture endurance is the characteristic which is required in not only a ferroelectric memory but also most semiconductor devices.
Therefore, in a multilayered wiring structure, the one provided with an SiN film between two wiring layers is also proposed. However, such a structure does not have sufficient moisture resistance.
Patent Document 1
    Japanese Patent Application Laid-open No. 2001-36026Patent Document 2    Japanese Patent Application Laid-open No. 2001-15703